The present invention relates, in general, to electronics, and more particularly, to methods of forming semiconductor devices and circuits.
In the past, the semiconductor industry utilized various methods and structures to determine the de-magnetization point of inductors that were utilized in power supplies and power supply controllers. Typically, transformers utilized in the power supply controllers had auxiliary windings that assisted in detecting the de-magnetization point. Examples of such implementations are disclosed in U.S. Pat. No. 5,784,231 issued to Majid et al on Jul. 21, 1998 and also in U.S. Pat. No. 5,892,355 issued to a Pansier et al on Apr. 6, 1999 both of which are hereby incorporated herein by reference. One problem with these prior techniques was the auxiliary windings and associated circuitry connected to the auxiliary inductor. The extra windings and circuitry increased the cost of the power supply system.
Another technique is disclosed in U.S. Pat. No. 6,469,484 issued to L'Hermite et al on Oct. 22, 2002 which is hereby incorporated herein by reference. This technique utilized additionally circuitry and had an associated cost.
Accordingly, it is desirable to have a method of detecting the de-magnetization point that does not use an auxiliary winding and that reduces the cost of the circuit and system.
For simplicity and clarity of illustration, elements in the figures are not necessarily to scale, and the same reference numbers in different figures denote the same elements. Additionally, descriptions and details of well known steps and elements are omitted for simplicity of the description. As used herein current carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor or an emitter or a collector of a bipolar transistor, and a control electrode means an element of the device that controls current through the device such as a gate of an MOS transistor or a base of a bipolar transistor. Although the devices are explained herein as certain N-channel or P-Channel devices, a person of ordinary skill in the art will appreciate that complementary devices are also possible in accordance with the present invention.